1. Field of the Invention
The present invention relates to cell selection in a wireless communication system. More particularly, the present invention relates to a method and apparatus for, upon network entry, efficiently selecting a cell in a wireless environment in which a plurality of femto cells, pico cells, and repeaters coexist within a macro cell.
2. Description of the Related Art
In a cellular communication network, for example, in an Orthogonal Frequency Division Multiple Access (OFDMA) communication network, a Base Station (BS) exists in every cell and performs communication with at least one Mobile Station (MS) within the cell. When the MS first operates (or the MS powers on), the MS performs an initial cell search and connects with the cellular communication network. The initial cell search includes a downlink synchronization procedure between the BS and the MS, in which the BS transmits a synchronization signal to the MS. The synchronization signal is called a preamble, a synchronization channel or a cell identifier (or a preamble identifier). Also, the synchronization signal may include one synchronization channel, or include a 1st synchronization channel and a 2nd synchronization channel, or include one long preamble and a plurality of short preambles. Each BS within an area has a unique preamble or a cell identifier.
On the other hand, various types of small BSs (i.e., pico cells and femto cells) coexist within constant coverage and are used in order to increase system capacity in a cellular communication network. That is, a pico BS covering a pico cell, a femto BS covering a femto cell, and the like are called small BSs. The small BS expands indoor coverage, improves call quality, and more efficiently provides various wired/wireless fusion services. In this wireless communication system in which a plurality of small BSs coexist within a macro cell, the total system capacity may be improved.
However, despite the fact that various types of small BSs should be efficiently used in a wireless communication system covered by a macro BS, there is currently no sufficient method for performing this function. For instance, BSs of various forms may generally coexist within the service coverage area of a macro BS. In this case, when using an existing BS selection method, an MS typically selects the macro BS, making it impossible to achieve the original purpose of improving the total system capacity. Here, the existing BS selection method is a method of selecting a BS with a high reception strength based on a reception strength of a preamble (i.e., a signal including a synchronization and BS identifier) of each BS. However, including various types of BSs within a macro BSs service coverage area as described above is for increasing the total system capacity. To achieve this purpose, it should be allowed for MSs within the macro BSs service coverage area to be able to select any of the various types of BSs most effectively.
Accordingly, there is a need for a method and apparatus for efficiently selecting a cell in a wireless communication system in which a plurality of femto cells, pico cells, and repeaters coexist within a macro cell.